This invention relates to an exhaust system for a small boat and more particularly to an improved exhaust system for a small boat that will preclude water from re-entering the exhaust system in the vicinity of the exhaust ports in the event the boat is inverted and subsequently righted.
As is well known, many types of watercraft have their engines and exhaust systems disposed so that the exhaust gases are discharged to the atmosphere in close proximity to or even below the water level. In addition, it is also the practice to discharge the cooling water from the engine into at least a portion of the exhaust system so that it will be discharged back to the body of water in which the watercraft is operating along with the exhaust gases.
Many types of watercraft are quite sporting in their nature and it is anticipated that the watercraft may easily become capsized. These same watercraft are designed so that once capsized they will either be self-righting or can be easily righted. If the exhaust gases are discharged in close proximity to the water level, the inversion of the watercraft can cause water to enter the exhaust system through the exhaust outlet. When the watercraft is righted, this water may flow back through the exhaust system and enter the engine through its exhaust ports. Also, if the exhaust system includes a catalyzer, the catalyzer is normally positioned in close proximity to the exhaust ports and any water that may enter the exhaust system can seriously damage the catalyzer.
It has been proposed, therefore, to provide a device known as a water trap which is located in the exhaust system and which serves the purpose of trapping water in the event the watercraft is capsized and then righted so that the trapped water can again be returned to the body of water in which the watercraft is operating when the engine runs.
FIG. 1 shows a prior art construction of this type wherein an internal combustion engine of a known type is identified generally by the reference numeral 11 and has exhaust ports 12 that discharge the exhaust gases into a combined exhaust manifold and expansion chamber 13. An exhaust elbow, indicated generally by the reference numeral 14 has an internal passage 15 that communicates with the exhaust manifold 13 and delivers the exhaust gases to an expansion chamber 16 of a second expansion chamber device 17. The exhaust gases are discharged from the second expansion chamber device 16 through a further exhaust conduit 18 having a passage 19 which communicates with a water trap device, indicated generally by reference numeral 21.
The water trap device 21 is comprised of a box like configuration which is divided into an inlet chamber 22 and a discharge chamber 23 by an internal wall or baffle 24. The chambers 22 and 23 communicate with each other through a passage 25 in the wall 24. An inlet fitting 26 having a generally right angle configuration and facing downwardly receives the exhaust gases from the conduit 18 and they enter the chamber 22. These exhaust gases then flow through the opening 25 into the chamber 23 for discharge through an exhaust discharge conduit 27 which also has a right angle configuration and faces downwardly. A flexible exhaust conduit 28 connects the discharge 27 to the atmosphere in proximity to the water level.
With this type of device, if the watercraft in which the system described is inverted and the outlet end of the conduit 28 becomes submerged, water will flow into the water trap device 21. However, the device 21 has sufficient volume so that any water which fills it when inverted will not enter the opening of the exhaust inlet conduit 26. Hence, when the watercraft is righted, water will not flow back through the exhaust system described to the exhaust ports 12 of the engine.
In addition to the construction of the prior art as thus far described, it is also conventional in watercraft propulsion units of the type described to discharge the coolant from the cooling jacket of the engine 11 back to the body of water in which the watercraft is operating through the exhaust system. Frequently, certain components of the exhaust system and particularly those in close proximity to the engine, such as the exhaust manifold 13, exhaust elbow 14 and expansion chamber device 17 are provided with respective cooling jackets through which this coolant flows. These cooling jackets are indicated respectively at 29, 31 and 32. These cooling jackets are formed primarily by double wall construction. It should be seen that the expansion chamber device 16 has an outlet portion 33 which communicates with the exhaust conduit 18 and also the water from the cooling jacket 32 can enter the exhaust system at this point.
When the engine is running this type of system is quite effective. However, if the watercraft becomes inverted the engine will be stopped and this means that water from the cooling jackets can re-enter the exhaust conduits through the opening 33 and could enter the exhaust ports 12. In addition, if there is provided a catalyzer in the exhaust system, it will be positioned in this area since it is desirable to maintain it in close proximity to the engine exhaust ports and hence the catalyzer may be damaged.
It is, therefore, a principal object of this invention to provide an improved exhaust system for a small boat wherein it will be insured that water cannot enter the engine or impinge upon a catalyzer in the exhaust system in the event the watercraft is inverted and righted.
It is a further object of the invention to provide an arrangement wherein engine coolant is discharged into the exhaust gases but this engine coolant also is precluded from entering the exhaust system in the event the watercraft becomes inverted and re-righted.
It is a still further object of this invention to provide an improved exhaust system for a small watercraft wherein water entry to the engine or impingement on the catalyst bed is precluded.